Question

EXPERIMENT 10 ACID AND BASE TITRATION 2 Post - Laboratory Questions 1. Student A weighs 0.747 g of KHP on a laboratory balance. The KHP was titrated with an unknown NaOH solution and the concentration of the NaOH was determined to be 0.113 M. Student B diluted 6 M HCl from the reagent shelf using a volumetric flask to obtain 0.6 MHCI. This solution was titrated with the same unknown NaOH solution and found to be 0.104 M. Which student should have the more accurate concentration for the unknown NaOH? Why?

Answer 1

A primary standard is a substance that can be prepared accurately and its concentration is accurate when prepared by weighing its accurate amount. A secondary standard is a substance whose concentration keeps on changing (decreasing) with time hence all the secondary standard substances need to be standardize by its titration with a primary standard to know its exact concentration before use in the laboratory. KHP is a primary standard while both NaOH and HCl are secondary standards. Hence, student A have the more accurate concentration as Student A did standardize NaOH using a primary standard.